The present invention relates to a gas insulated switchgear for a private-use high voltage power receiving/transforming apparatus.
As to conventional gas insulating switchgears for private-use high voltage power receiving/transforming apparatus, two types, referred to as one-measuring-circuit type and two-measuring-circuit type, are known according to the difference in the method of measuring the amount of consumed electric power. The former type has a construction in which electric power is received with two lines and led to two transformers through one instrument potential/current transformer as described in Japanese Patent Application Laid-Open No. 1-303002 (1989). Therefore, although the reliability of electric power supply is improved with the double-receiving circuit, the electric line should be completely shut down at the time when the instrument potential/current transformer is inspected or replaced. On the contrary, the latter type has two instrument potential/current transformers as described in Japanese Patent Application Laid-Open No. 1-248911 (1989), and when one of the instrument potential/current transformers is inspected, the consuming electric power is measured using the other instrument potential/current transformer to avoid the complete power outage.
However, in a case where two instrument potential/current transformers are used, there arise problems due to the increase in the size of the gas insulated switchgear, and the increase in work for inspection and maintenance of the instrument potential/current transformers. Therefore, there is proposed a bypass disconnecting switch type where one of the two instrument potential/current transformers in the two-measuring-circuit type is replaced with a bypass disconnecting switch. That is, as shown in FIG. 17, an instrument potential/current transformer 13 and a bypass disconnecting switch 32 are connected in parallel, and when the instrument potential/current transformer is inspected or replaced, the bypass disconnecting switch 32 is connected to continue operation. The amount of consumed electric power during the time is determined by performance figures in the past to avoid the complete power outage.
By employing the bypass disconnecting switch type using one instrument potential/current transformer, inspection and replacement of the instrument potential/current transformer can be performed without power outage as described above.
FIG. 18 is a plan view of the private-use high voltage power receiving apparatus of FIG. 17 which is constructed based on a conventional technology. In this figure, a closed loop composed of an instrument potential/current transformer unit 13 and a bypass disconnecting switch 32 is constructed on a plane, which makes the size of the gas insulated switchgear large. On the other hand, in the gas insulated switchgear shown in FIG. 20, a closed loop composed of an instrument potential/current transformer unit 13 and a bypass disconnecting switch 32 is three-dimensionally constructed in two stages, upper and lower stages, to enable decreasing the size of the gas insulated switchgear. However, when an additional transformer-side unit is added by adding a bank in this construction, it is difficult to add the bank since the existing transformer-side unit is arranged in the inner side of the power receiving unit and the power receiving unit interferes the connection between the added transformer-side unit and the existing transformer-side unit.